1. Field of the Invention
The present invention is directed to a process for temperature stabilization of a reference voltage and, in particular, to a process in which, in a first time interval, a current with a first amperage and, in a second time interval, a current with a second amperage are alternately provided to a diode or pn junction, preferably the base-emitter diode of a bipolar transistor. During the first and second time intervals, the voltages at the diode or the pn junction are supplied to the input of an analysis circuit. In the analysis circuit, the difference between the two voltages obtained through the first and the second amperages is formed and added in a weighted manner to the voltage obtained through one of the two amperages. The result is then provided as the output of the analysis circuit.
2. Description of the Related Art
Bandgap reference processes based on the principle of temperature compensation through weighted addition of two voltages U1 and U2 with opposing temperature coefficients are well known. The weighting factors K1 and K2 are chosen in such a way that the effects on these voltages due to the temperature T mutually cancel each another. The reference voltage Uref is thus represented as follows: EQU Uref=K1U1(T)+K2U2(T)
U.S. Pat. No. 5,059,820 discloses a circuit configuration in accordance with such a known bandgap reference process in which, for temperature stabilization of a reference voltage, two different amperages are alternately provided, by means of two synchronized current sources, to a single pn junction formed by the base-emitter diode of a bipolar transistor. The voltage drop at the pn junction is supplied to an analysis circuit. In this way, owing to the use of only one diode, it is not necessary to take into account variation or scatter of the characteristic data of a second diode. It is thereby possible to greatly reduce the scatter of the absolute value of the reference voltage as well as its temperature dependence. A particular advantage of this process is that it is only weakly dependent on resistance relations and current density relations.
PCT Patent Application WO 82/02806 discloses that, for the voltages U1 and U2 with opposed temperature effect, it is known to use the voltage drop U.sub.be at the base-emitter diode of a bipolar transistor, given the current density and the voltage difference DU.sub.be between these and the base-emitter diode of another bipolar transistor, to which a different amperage is applied. The weighted addition of the voltages U1 and U2 occurs in an analysis circuit by means of an operational amplifier connected to resistors.
The drawbacks of this process lie, first, in the use of at least two base-emitter diodes, since very different results can thereby be obtained due to scatter of the characteristic data, and, second, in the poor implementation of the process in the case of integrated circuits in CMOS technology, since the resistors of the analysis circuit in this technology cannot be fabricated with adequate precision.